Re: Berserk Autovacuum (let's save next Mandrill)

On Tue, Mar 17, 2020 at 08:42:07PM +0100, Laurenz Albe wrote:
> Also, since aggressive^H^H^H^H^H^H^H^H^H^Hproactive freezing seems to be a
> performance problem in some cases (pages with UPDATEs and DELETEs in otherwise
> INSERT-mostly tables), I have done away with the whole freezing thing,
> which made the whole patch much smaller and simpler.
>
> Now all that is introduced are the threshold and scale factor and
> the new statistics counter to track the number of inserts since the last
> VACUUM.
>
> Updated patch attached.
>
> Perhaps we can reach a consensus on this reduced functionality.

+1

I still suggest scale_factor maximum of 1e10, like
4d54543efa5eb074ead4d0fadb2af4161c943044

Which alows more effectively disabling it than a factor of 100, which would
progress like: ~1, 1e2, 1e4, 1e6, 1e8, 1e10, ..

I don't think that 1e4 would be a problem, but 1e6 and 1e8 could be. With
1e10, it's first vacuumed when there's 10billion inserts, if we didn't previous
hit the n_dead threshold.

I think that's ok? If one wanted to disable it up to 1e11 tuples, I think
they'd disable autovacuum, or preferably just implement an vacuum job.

The commit message says:
|The scale factor defaults to 0, which means that it is
|effectively disabled, but it offers some flexibility
..but "it" is ambiguous, so should say something like: "the table size does not
contribute to the autovacuum threshold".

--
Justin